Bisulfite ion (the aqueous form of the atmosphere pollutant, sulfur dioxide) has a number of reactions with the nucleic acids. We wish to determine the extent to which these reactions contribute to the biological damage caused by sulfur dioxide. We plan to work on several levels, including reactivity studies on nucleosides and polynucleotides, studies on the transcription and translation of modified polynucleotides, and investigations involving chromatin, E. coli and mammalian cells in culture. The specific questions that we hope to answer include the following: (1) What is the rate of bisulfite-catalyzed deamination of cytosine in DNA and chromatin? Does this reaction have significance for environmental mutagenesis? (2) Could alternative pathways, such as the formation of cytosine-bisulfite adducts, or transamination be responsible for bisulfite mutagenesis in vivo? (3) Does the treatment of chromatin with bisulfite cause protein-nucleic acid cross-linking? (4) Do free radical reactions of bisulfite cause DNA damage in vivo? (5) What is the mechanism of bacterial growth inhibition by bisulfite? We wish, in addition, to use bisulfite as a tool in model studies on carcinogesis and in developing new synthetic reactions of biochemical utility. Progress in this research, and in related studies by others, will be summarized in reviews and reports to federal regulatory agencies.